1. Field of the Invention
The present invention relates to a method for forming external screw threads using flat dies, and more particularly to a thread rolling method for producing a variety of screw threads of different characteristics using one type of thread rolling die.
2. Description of the Prior Art
In forming screw threads using thread rolling flat dies, it has been customary to prepare flat dies designed to meet the characteristics of the screw threads to be produced. These characteristics include thread size, spacing, shape, dimensions and screw diameter. The flat dies are then attached to a pair of sliding mechanisms which move in synchronism with each other in a thread rolling machine. A workpiece is positioned supported by a centering mechanism between the sliding mechanisms. These sliding mechanisms (sliding means) are then moved in a thread rolling direction so as to be pressed against the workpiece so that threads are cut in the workpiece.
With the above conventional method, however, the flat dies must be replaced with other flat dies when it is desired to form screw threads of different characteristics. Production of various screw threads has therefore required that thread rolling dies be replaced many times during the process. This has led to drawbacks in that the rate of production cannot be increased, and the cost of manufacturing screws is raised.